This invention relates to a method of treating fibrous materials to improve the flame retardant properties thereof, and to fibrous cellulosic materials which have been treated in accordance with the invention. More particularly, this invention relates to the use of particular antimony compounds for improving the flame-retardant properties of fibrous textile fabrics containing at least some cellulose.
Various fibrous textile materials such as cotton goods present an appreciable fire hazard due to the ease with which they can be ignited. The potential fire hazard has drawn considerable interest, and many suggestions have been made for improving the properties of textiles and reducing the fire hazard. This is particularly true in clothing and in carpeting.
Various compounds have been added to or incorporated into textile materials in an attempt to reduce the fire hazard when such materials are ignited. It is now well known that halogen-containing organic materials impart effective levels of flame retardancy to many textile materials particularly to synthetic organic polymers used in the formation of textile fabrics and carpeting. A number of metal compounds also have been reported in the literature as flame retardants for various substrates, and by far, the best known prior art compounds are compounds of antimony such as antimony oxides and antimony oxychloride. Other metal compounds which have been suggested as being useful fire retardants include the phosphates and borates of alkali and alkaline earth metals, titanium salts, tin salts, etc.
The most widely employed technique for improving the fire retardant properties of textile materials comprises impregnating and/or coating the textile with a combination of a halogenated resin or paraffin and an inorganic oxide material. Antimony compounds, such as antimony trioxide reportedly act as synergists with halogen-containing compounds at flame temperatures in that they significantly improve the flame retardancy imparted to the textile material at a given concentration of halogen compounds. This synergistic improvement is surprising since antimony oxides are ineffective when used alone. See, for example, U.S. Pat. No. 3,892,667 and Flame Resistant Cotton, W. A. Reeves and G. L. Drake (1971, page 50). U.S. Pat. No. 3,860,523 describes colloidal antimony oxide sols which are suited for use with organic halogens such as polyvinyl chloride for improving the flame retardant properties of fabrics.
The use of the combination of a halogenated resin or paraffin with an inorganic oxide material may change the character of the textile because of the coating which may reduce the flexibility of the textile. Also, although such coatings are relatively water-resistant, they are generally not resistant to solvents such as used in dry-cleaning thereby limiting the usefulness of such treatments. Moreover, the requirement that the antimony oxides be used in combination with halogenated resins or paraffins adds to the cost of the fire-retardant treatment.
In U.S. Pat. No. 3,468,844, thermoplastic polyarylene polyethers are rendered flame retardant by incorporating effective amounts of antimony trioxide (Sb.sub.2 O.sub.3). U.S. Pat. No. 3,892,667 describes the use of the combination of sodium antimonate and inorganic chlorine- or bromine-containing compounds as a flame retardant composition for synthetic organic polymer compositions. The patentees indicate that the sodium antimonate particles should contain at most, insignificant amounts of water-soluble alkaline materials. In U.S. Pat. No. 2,805,176, it is suggested that artificial materials or products of the viscose cellulose type such as viscose rayon can be flame-proofed by incorporating therein, a compound of a metal which can react with selected reactive groups within the viscose to produce an insoluble compound of the metal embodied within the cellulose fiber. Compounds of antimony, zirconium, tin, tungsten and titanium are described. For example, treating an unrelaxed viscose fiber containing a minor percentage of carboxy methyl cellulose with an appropriate antimonate results in the formation of an insoluble, hydrated antimony oxide or antimonic acid which is retained by the regenerated cellulose body.
British Pat. No. 579,328 describes a method of applying antimony compounds to fabrics and fibers to render them fire-resistant. The method described comprises impregnating the fibers or fabrics with a potassium antimonate and subsequently precipitating antimony oxide in the fiber by treatment with a salt of a strong acid and a weak base such as ferrous sulfate. The fire-proofing obtained in this manner is reported to be substantially resistant to removal by washing with water.